The present invention relates to an apparatus for generating a hydrogen gas to be supplied to appliances that use hydrogen such as fuel cells from water and a hydrocarbon type fuel such as natural gas, liquefied petroleum gas, gasoline, naphtha or kerosene used as raw materials.
Recently, hydrogen gas has drawn much attention as a convincing alternative energy source to replace a fossil fuel. For an efficient use of hydrogen, it is necessary to prepare a so-called industrial infrastructure such as pipelines for hydrogen.
From such a point of view, it has been proposed to use an infrastructure for transporting natural gas, fossil fuel, alcohol or the like and reform these fuels to generate hydrogen in the place where hydrogen is needed. For example, techniques for reforming natural gas (city gas) to be supplied to fuel cells used as a medium and small-scale on-site power generator and techniques for reforming methanol to be supplied to fuel cells used as a power source for cars have been proposed in various manners.
On the other hand, the technique for solid polymer fuel cells has remarkably been developed in recent years and such fuel cells are considered to be suitable for small scale use because they can operate under low temperature, start-up quickly and have less heat loss. For such a reason, these fuel cells are expected to further develop into automobile and domestic use.
In order to meet such an expectation, a small-size hydrogen generator for supplying hydrogen to solid polymer fuel cells has vigorously been developed in various quarters. However, an apparatus that sufficiently meets the demand has not been commercially available yet.
It should be noted that as the method for generating hydrogen from a hydrocarbon type fuel such as natural gas, a partial oxidation method, a steam reforming method and a use of both methods together are known. However, each of them has advantages as well as disadvantages and they are chosen according to the object of the system including fuel cells that use hydrogen to be generated. In general, the steam reforming method can generate a gas having the highest concentration of hydrogen; therefore a high generation efficiency of the fuel cells can be estimated. In order to reform the fuels as described above, a catalytic reaction under high temperature is employed in any of the above methods.
A conventional hydrogen generator for fuel cells has usually been in a scale where the output of fuel cells can be brought to not less than several hundred kW, therefore an apparatus that can supply to fuel cells in the level of between several hundred W and several kW, which is suitable for domestic or portable use, has been difficult to produce until now.
This is because the proportion of the surface of the hydrogen generator to its volume becomes large as the scale of the apparatus becomes small and consequently the rate of the heat dissipation loss from the surface of the apparatus becomes large; as a result, the heat efficiency is impaired.
In other words, there is a problem that a decrease in efficiency of the hydrogen generator itself leads to a decrease in efficiency of the system including fuel cells, so the heat efficiency of the hydrogen generator needs to be improved in order to realize a small-size system including fuel cells. Especially when natural gas is used as the fuel, a high temperature of around 700xc2x0 C. is required as the reaction temperature; therefore, in view of heat utilization, a heat insulating constitution for reducing the heat dissipation loss and a method for collecting and using waste heat are considered to be the most important points.
Considering the facts as described above, an object of the present invention is to provide a hydrogen generator having a simple structure that can, in particular, collect and efficiently use waste heat to significantly improve the heat efficiency.
The present invention is related to a hydrogen generator for generating a hydrogen gas, comprising at least a fuel supply part for supplying a hydrocarbon type fuel, a fuel combustion part, a water supply part, a gas mixing part for mixing the fuel and a water, and a reforming part filled with the reforming catalyst, wherein at least one of the gas mixing part and the reforming part is heated by an exhaust gas generated in the fuel combustion part.
In concrete, the present invention related to a hydrogen generator for generating a reformed gas containing hydrogen from a gas mixture to be reformed by catalysis of a reforming catalyst, comprising at least a fuel supply part for supplying a hydrocarbon type fuel, a fuel combustion part, a water supply part, a gas mixing part for preparing the above gas mixture to be reformed by mixing the above fuel and a water, and a reforming part filled with the above reforming catalyst, wherein at least one of the above gas mixing part and the above reforming part is heated by an exhaust gas generated in the above fuel combustion part.
In other words, the hydrogen generator of the present invention has a constitutional structure so that at least one of the gas mixing part and the reforming part can be heated by an exhaust gas generated in the fuel combustion part.
It is preferable that a water vaporization part is placed between the water supply part and the gas mixing part and the water vaporization part is heated by the exhaust gas generated in the fuel combustion part.
Further, it is preferable that an air to be supplied to the fuel combustion part is heated by combustion heat of the fuel combustion part.
In addition, it is preferable that a pre-heating part for heating at least one of the hydrocarbon type fuel and the air to be supplied to combustion is provided on the periphery of the fuel combustion part.
Moreover, it is preferable that the flow of the exhaust gas and the flow of a mixed gas of the fuel and the water to be reformed are placed at reverse direction with each other.
In other words, it is preferable that the flow direction of the exhaust gas and the flow direction of the gas mixture to be reformed are counter to each other.